Cooking Oil Recycled From Sewers—It’s as Gross as It Sounds and More Common Than You’d Think

China has a gutter oil problem, and it is not going away. The market for gutter oil—cooking oil made from restaurant waste and the scrapings of gutters and sewers that is being mass-produced in China—is thriving.

The disgusting recycling process is intricate. Restaurants sell their waste to pig farms. There, it is boiled. The floating oil at the top is sold to small oil collectors and the solid residue is used as pig feed. The small oil collectors sell the waste oil to large oil collectors, who then sell it to refineries. Refineries process the oil product and peddle it back to restaurants and supermarkets.